Add dataset route for RPB
Add serve JSON-LD when requesting a dataset

* add dataset routes NWbib and RPB
Merge branch 'master' into issue-422-config-play
Add lobid persons routes

* refactor a bit
Simplify the elasticsearch requests due to a comment by @fsteeg
Merge pull request #425 from lobid/issue-422-config-play

Issue #422: config play for dataset descriptions and persons